Robot Arm Input Shaping Across Joint and Cartesian Spaces

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Solution Overview

Problem

Existing robot arm control methods face challenges in suppressing vibrations effectively, particularly when transitioning between joint space and Cartesian space motions, leading to deviations from the intended path and reduced performance.

Innovation Solution

A robot controller that utilizes input shaping by convolving target motions in both joint and Cartesian reference spaces, allowing dynamic adjustment and blending between these spaces to reduce positional deviations and enable seamless transitions without standstill.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If input shaping is applied in joint space to suppress vibrations, then vibration suppression is improved, but Cartesian path accuracy deteriorates due to deviations from the intended path

Engineering Contradiction:

Improvevibration suppressionVSAvoidCartesian path accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The system dynamically switches between joint space input shaping and Cartesian space input shaping based on the current motion mode. When the robot operates in joint space motion, joint space input shaping is applied; when operating in Cartesian space motion, Cartesian space input shaping is applied. This dynamic adaptation resolves the contradiction by ensuring that the appropriate input shaping method is used for each motion type, maintaining both vibration suppression and path accuracy.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control parameter being changed is the reference space in which input shaping is applied. The system transforms the input shaping operation from a fixed joint space approach to a flexible parameter that can be switched between joint space and Cartesian space depending on the motion requirements, thereby resolving the trade-off between vibration suppression and path accuracy.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the robot transitions between joint space and Cartesian space motions, then motion flexibility is improved, but vibration suppression performance deteriorates due to path deviations

Engineering Contradiction:

Improvemotion flexibilityVSAvoidvibration suppression performance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system implements dynamic switching between joint space input shaping and Cartesian space input shaping based on the current motion mode. The controller detects whether the robot is executing joint space motion or Cartesian space motion and applies the corresponding input shaping method, ensuring continuous effective vibration suppression while maintaining motion flexibility across different reference spaces.

Inventive Principle:

Principle #15Dynamics

3Ease of operation

If light-weight design is implemented to enable collaborative robot interaction, then safety and ease of operation are improved, but mechanical rigidity deteriorates leading to increased vibrations

Engineering Contradiction:

Improvecollaborative interaction safetyVSAvoidmechanical rigidity

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The system applies input shaping as a preliminary anti-action to counteract the vibrations that arise from the light-weight design. By convolving the target motion with an impulse train designed to counteract the robot arm's vibration modes, the system proactively suppresses vibrations before they affect collaborative interaction safety, thereby compensating for the reduced mechanical rigidity.

Inventive Principle:

Principle #9Preliminary anti-action

4Productivity

If seamless transitions between joint space and Cartesian space are enabled without standstill, then productivity is improved, but control complexity increases

Engineering Contradiction:

Improvetransition efficiencyVSAvoidcontrol system complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The control system dynamically adapts the input shaping reference space based on the current motion mode, enabling seamless transitions between joint space and Cartesian space without requiring standstill. The controller switches between joint space input shaping and Cartesian space input shaping formulations, maintaining continuous vibration suppression while allowing flexible, efficient transitions that improve productivity without requiring the system to come to a complete stop.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS12350838B2Input shaping control of a robot arm in different reference spaces

Publication Date: 2025.07.08 UNIVERSAL ROBOT

AI summary

A robot controller for controlling a robot arm includes a first space shaping module configured to provide a shaped first space target motion by convolving a first space target motion with an impulse train, where the first space target motion defines a target motion in a first reference space; a second space shaping module configured to provide a shaped second space target motion by convolving a second target motion with the impulse train; where the second target motion defines the target motion in a second reference space; and a motor controller module to generate motor control signals to the joint motors based on the shaped first space target motion and the shaped second space target motion.